Chair frame



FIG. 1 is a front view of a chair frame showing my design;

FIG. 2 is a left side view of a chair frame showing my design, the other side being identical therewith;

FIG. 3 is a back view of a chair frame showing my design;

FIG. 4 is a top view of a chair frame showing my design; and

FIG.5 is a bottom view of a chair frame showing my design. 

The ornamental design for a chair frame, as shown and described. 